Greatly Enhanced Raman Scattering of Graphene on Metals by a Boron Nitride Film Covering

Raman spectroscopy, a nondestructive fingerprinting technique, is mainly utilized to identify molecular species and phonon modes of materials. However, direct Raman characterization of two-dimensional materials typically synthesized on catalytic metal substrates is extremely challenging because of the significant electric screening and interfacial electronic couplings. Here, we demonstrate that by covering as-grown graphene with boron nitride (BN) films, the Raman intensity of graphene can be enhanced by two orders of magnitude and is also several times stronger than that of suspended graphene. This great Raman enhancement originates from the optical field amplification by Fabry-Pérot cavity in BN films and the local field plasmon near copper steps. We further demonstrate the direct characterization of the local strain and doping level of as-grown graphene and in situ monitoring of the molecule reaction process by enhanced Raman spectroscopy. Our results will broaden the optical investigations of interfacial sciences on metals, including photoinduced charge transfer dynamics and photocatalysis at metal surfaces.